This proposal outlines a five-year career development and research plan to train the candidate as an independent epidemiologic investigator focused on outcomes research in international settings. The candidate's strong academic performance and international work on HIV-1 risk factors and transmission, including generalizability of prevention interventions, demonstrates his expertise in epidemiologic methodology and applied research. As a doctoral candidate, he led the epidemiologic design and analysis of a large prospective cohort study of discordant couples in Kenya. This research experience was enhanced by a postdoctoral fellowship in which he investigated barriers to timely initiation of antiretroviral therapy (ART) and developed mathematical models for the impact of the distribution of risk factors on generalizability of intervention trials. This K01 award will enablethe candidate to integrate this background into a new line of investigation on the implementation of behavioral interventions to promote HIV/AIDS care and treatment. The candidate will be supported by expert mentors to provide guidance and ensure the success of this project. An enriching institutional environment will support his career development. RESEARCH PLAN. Half of patients testing positive for HIV-1 at voluntary counseling and testing (VCT) centers in Sub-Saharan Africa fail to link with HIV/AIDS care. This highlights a critical deficiency in the health system that can be addressed with interventions to improve linkage to care that will slow disease progression, accelerate ART initiation, and improve health outcomes. We hypothesize that an implementation science approach will produce a package of interventions to improve linkage to care and treatment that will be rapidly scalable across sites in Africa. We will test a behavioral intervention and evaluate new point-of-care (POC) CD4 testing to improve linkage to care. The specific aims are to (1) determine if a VCT-based intervention of CD4 count testing, alone or in combination with peer counseling, improves linkage to HIV/AIDS care; (2) assess the impact of the intervention on ART initiation; and (3) determine if rapid return of CD4 results using new POC testing improves linkage to care compared to conventional testing with delayed return of results. First, we will conduct a rapid assessment of barriers to care among patients, counselors, and health providers to refine the intervention (VCT-based CD4 counts and peer counseling). We will then recruit 450 HIV-positive individuals from VCTs and randomize a third to standard counseling and referral, a third to receive CD4 testing at the VCT with results return by phone after two weeks, and a third to receive the same CD4 testing combined with peer counseling. We will recruit an additional 150 participants to receive POC CD4 testing with rapid return of results and compare their linkage to care rates to those receiving CD4 results after two weeks. These combined investigations will create a comprehensive understanding of obstacles to appropriate HIV/AIDS care and result in new interventions to achieve measurable outcomes in applied settings. Through this award the candidate will gain new expertise in implementation science and will become an independent investigator focused on health interventions in resource-limited settings. Public Health Relevance: Failure to link to HIV/AIDS care and start antiretroviral therapy in a timely manner leads to poor health outcomes in people living with HIV in Sub-Saharan Africa. A systematic approach is needed to identify barriers to appropriate care and treatment and to design, implement, and evaluate interventions that address these barriers. The proposed study will follow an implementation science framework to measure and overcome barriers to care and treatment at both the individual and the health system levels, and will result in an intervention package that is scalable and rapidly deployable.